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Shower problems

Help please my shower keeps tripping the rcd but not the breaker below are the facts
New shower Triton 8.5kw
6mm twin earth cable
Fitted in to a 40a breaker RCD = 30A 80Kw

As it is the shower in the bathroom is fed in to a pull switch and then in to the mains.

I have tried everything the power to the shower is on as the light on the shower comes on but as soon as you turn on to use it tripps the RCD and not the breaker , it is a brand new shower bought from Argos I originally thought that the shower was faulty so I took it back and got a brand new one today, fitted it and had the same problem

4 Answers from MyBuilder Electricians

Best Answer


Assuming that the shower is in a bathroom at home, you have unwittingly committed a criminal offence by fitting yourself. Legislation changed in 2005 to make it an offence for electrical work to be carried out in a special location without local building control notification. Some registered electricians can self-certify and notify. The important thing is the testing prior to energising, I am assuming that you do not have the training to do this, so you are putting yourself and the other members of the household at risk of electrocution and/or fire.

Back to your problem. I would not use 6mm for an 8.5Kw shower, I would not protect 6mm with a 40A MCB. If the RCD is not faulty it is doing its job and saving you.

Get someone in to test the wiring before you live to regret it. Make sure that they know what they are doing, ask for inspector level qualifications, most of us have them these days.


Answered 7th Jul 2015

Sounds like a faulty RCD! Does it say 80amp 30 MA on the RCD? Only way you will tell is to get a qualified electrician to come a test the circuit to make sure that's not at fault and also perform a RCD test.



Answered 7th Jul 2015

sounds like bad earth or faulty breaker, the electrician that wired the shower should easily identify the problem, be careful here lots of power around a water source


Answered 7th Jul 2015

There is a Neutral to Earth fault somewhere on the circuit between the shower switch and the shower. Could be burnt/damaged insulation at the switch terminations? or could be that the cable in the wall/ceiling is damaged. Best bet is to get an electrician in to carry out an insulation resistance test on the circuit and also check for earth leakage current.


Answered 7th Jul 2015

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